sub php_strstr {
  my $haystack      = shift;
  my $needle        = shift;
  my $before_needle = shift;

  my $i = index( $haystack, $needle );

  # needle not found
  if ( $i == -1 ) {
    return undef;                 # or maybe ''; it's FALSE in php
  }
  # return substring before needle
  elsif ( $before_needle ) {
    return substr( $haystack, 0, $i );
  }
  # return substring beginning with first found needle till end of string
  else {
    return substr( $haystack, $i );
  }
}